Non-contact diagnostic system for sleep apnea–hypopnea syndrome based on amplitude and phase analysis of thoracic and abdominal Doppler radars

Full-night polysomnography (PSG) has been recognized as the gold standard test for sleep apnea–hypopnea syndrome (SAHS). However, PSG examinees are physically restrained for the full night by many contact sensors and obtrusive connecting cables, inducing mental stress. We developed a non-contact SAHS diagnostic system that can detect apneic events without inducing stress in monitored individuals. Two Doppler radars were installed beneath the mattress to measure the vibrations of the chest and abdomen, respectively. Our system determines apnea and hypopnea events when the radar output amplitude decreases by <20 and 70 %, respectively, of the amplitude of a normal breath (without SAHS events). Additionally, we proposed a technique that detects paradoxical movements by focusing on phase differences between thoracic and abdominal movements, and were able to identify three types of sleep apnea: obstructive, central, and mixed. Respiratory disturbance indexes obtained showed a higher correlation (r = 94 %) with PSG than with pulse oximetry (r = 89 %). When predicting the severity of SAHS with an apnea–hypopnea index (AHI) of >15/h or >30/h using PSG as a reference, the radar system achieved a sensitivity of 96 and 90 %, and a specificity of 100 and 79 % with an AHI of >15/h and >30/h, respectively. The proposed radar system can be used as an alternative to the current airflow sensor, and to chest and abdomen belts for apnea–hypopnea evaluation.

[1]  Wansuree Massagram,et al.  Tidal Volume Measurement Through Non-Contact Doppler Radar With DC Reconstruction , 2013, IEEE Sensors Journal.

[2]  C. Newth,et al.  Assessment of thoraco-abdominal asynchrony. , 2009, Paediatric respiratory reviews.

[3]  H Nakano,et al.  Automatic detection of sleep-disordered breathing from a single-channel airflow record , 2007, European Respiratory Journal.

[4]  T. Young,et al.  The occurrence of sleep-disordered breathing among middle-aged adults. , 1993, The New England journal of medicine.

[5]  V. Kapur,et al.  Obstructive sleep apnea devices for out-of-center (OOC) testing: technology evaluation. , 2011, Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine.

[6]  T. Keens,et al.  Rib cage to abdominal asynchrony in children undergoing polygraphic sleep studies , 1991, Pediatric pulmonology.

[7]  Roberto Hornero,et al.  Utility of Approximate Entropy From Overnight Pulse Oximetry Data in the Diagnosis of the Obstructive Sleep Apnea Syndrome , 2007, IEEE Transactions on Biomedical Engineering.

[8]  M Kagawa,et al.  Non-contact heart rate monitoring method for elderly people In bed with random body motions using 24 GHz dual radars located beneath the mattress In clinical settings , 2012, Journal of medical engineering & technology.

[9]  J. Victor Marcos,et al.  Linear and nonlinear analysis of airflow recordings to help in sleep apnoea–hypopnoea syndrome diagnosis , 2012, Physiological measurement.

[10]  E. Chiner,et al.  Nocturnal oximetry for the diagnosis of the sleep apnoea hypopnoea syndrome: a method to reduce the number of polysomnographies? , 1999, Thorax.

[11]  J. Stradling,et al.  Which derivative from overnight oximetry best predicts symptomatic response to nasal continuous positive airway pressure in patients with obstructive sleep apnoea? , 2000, Respiratory medicine.

[12]  Karen A. Brown,et al.  Automated estimation of the phase between thoracic and abdominal movement signals , 2005, IEEE Transactions on Biomedical Engineering.

[13]  Najib T. Ayas,et al.  Nasal pressure recordings to detect obstructive sleep apnea , 2006, Sleep and Breathing.

[14]  W. Flemons,et al.  Home diagnosis of sleep apnea: a systematic review of the literature. An evidence review cosponsored by the American Academy of Sleep Medicine, the American College of Chest Physicians, and the American Thoracic Society. , 2003, Chest.

[15]  Jenshan Lin,et al.  Range correlation and I/Q performance benefits in single-chip silicon Doppler radars for noncontact cardiopulmonary monitoring , 2004, IEEE Transactions on Microwave Theory and Techniques.

[16]  A. Malhotra,et al.  Clinical guideline for the evaluation, management and long-term care of obstructive sleep apnea in adults. , 2009, Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine.

[17]  G Kim Prisk,et al.  Techniques for measurement of thoracoabdominal asynchrony , 2002, Pediatric pulmonology.

[18]  C. Brambilla,et al.  Accuracy of oximetry for detection of respiratory disturbances in sleep apnea syndrome. , 1996, Chest.

[19]  Roberto Hornero,et al.  Pattern recognition in airflow recordings to assist in the sleep apnoea–hypopnoea syndrome diagnosis , 2013, Medical & Biological Engineering & Computing.

[20]  Carlo Atzeni,et al.  Non-Contact Detection of Breathing Using a Microwave Sensor , 2009, Sensors.

[21]  Toshimitsu Shinohara,et al.  Effect of body mass index on overnight oximetry for the diagnosis of sleep apnea. , 2004, Respiratory medicine.

[22]  Hugues Bersini,et al.  Detection of obstructive apnea events in sleeping infants from thoracoabdominal movements , 2002, Journal of sleep research.

[23]  S. Quan,et al.  Rules for scoring respiratory events in sleep: update of the 2007 AASM Manual for the Scoring of Sleep and Associated Events. Deliberations of the Sleep Apnea Definitions Task Force of the American Academy of Sleep Medicine. , 2012, Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine.

[24]  B A Staats,et al.  Chest wall motion in sleep apnea. , 1984, The American review of respiratory disease.

[25]  L. Hang,et al.  Comparison of the indices of oxyhemoglobin saturation by pulse oximetry in obstructive sleep apnea hypopnea syndrome. , 2009, Chest.

[26]  G Gennser,et al.  Phase characteristics of breathing movements in healthy newborns. , 1983, Journal of developmental physiology.

[27]  S. George,et al.  Evaluation of the accuracy of manual and automatic scoring of a single airflow channel in patients with a high probability of obstructive sleep apnea , 2011, Medical science monitor : international medical journal of experimental and clinical research.

[28]  Zahra Moussavi,et al.  Sleep apnea monitoring and diagnosis based on pulse oximetery and tracheal sound signals , 2010, Medical & Biological Engineering & Computing.